1. Field
This disclosure relates generally to generating electronic timing signals, and more specifically, to generating timing signals with changeable frequencies to control digital processing circuits.
2. Related Art
Reference clock generators produce timing signals that are used to clock the operation of digital circuits. Some devices incorporating digital circuits operate in different modes and each mode may have its unique processing requirements. In some applications, different modes operate more beneficially if a reference clock frequency is changed based upon a current mode of a device. One example of such a device is a wireless communications device that is able to process multiple types of wireless communications signals. Digital processing circuits for one type of signal may operate more efficiently if a variable reference clock generator is provided to change the reference clock frequency based upon the current mode of the device. Some devices benefit from reference clock generators that are able to change their output frequency but maintain phase synchronization when they return to their original output frequency.
Applications that benefit from variable reference clock generators that maintain phase synchronization include circuits that perform processing of signals with circuits based on a first clock frequency and that are desired to remain in synchronization with input signals during a time that the reference clock frequency is shifted to a second clock frequency.